MIPS Compiler

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# MIPS Compiler
<br /><br />
#### Adi Yoga S. Prabawa.red[*]

.footnote[.red[*] email me at dcsaysp (at) nus.edu.sg<br />if you find any bug or you want to work on this]

---

# Workspace

.left-column[
#### Overview
]
.right-column[
.image-100[![Workspace](./img/comp_01.png)]

MIPS interpreter workspace is divided into 8 areas in the same way as [MIPS interpreter](_interpreter.html#2)
]

---

# MipC Language

.left-column[
#### Grammar
]
.right-column[
The basic grammar of MipC is shown below:

<pre>
.mediumtext[
assg := reg = num
      | reg = hex
      | reg = reg op reg
      | reg = reg op num
      | reg = reg op hex
mems := reg = reg[num]
      | reg[num] = reg
seln := if (reg == reg) { stmt }
      | if (reg == reg) { stmt } else { stmt }
      | if (reg != reg) { stmt }
      | if (reg != reg) { stmt } else { stmt }
iter := wlop | flop | dlop
dlop := do { stmt } while (reg == reg);
      | do { stmt } while (reg != reg);
wlop := while (reg == reg) { stmt }
      | while (reg != reg) { stmt }
flop := for(assg; reg == reg; assg) { stmt }
      | for(assg; reg != reg; assg) { stmt }
stmt := assg | seln | iter
]
</pre>
]

---

# MipC Language

.left-column[
#### Grammar
#### Arithmetic & Logic
]
.right-column[
MipC has the following arithmetic and logic operations with the corresponding MIPS instructions.

.smalltext[
<table class="table table-sm">
  <thead class="table-secondary">
    <tr>
      <th scope="col">Operation</th>
      <th scope="col">MipC</th>
      <th scope="col">MIPS</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th scope="row"><i>Addition</i></th>
      <td><samp>$rd = $rs + $rt</samp></td>
      <td><samp>add $rd, $rs, $rt</samp></td>
    </tr>
    <tr>
      <th scope="row"><i>Subtraction</i></th>
      <td><samp>$rd = $rs - $rt</samp></td>
      <td><samp>sub $rd, $rs, $rt</samp></td>
    </tr>
    <tr>
      <th scope="row"><i>Bitwise AND</i></th>
      <td><samp>$rd = $rs & $rt</samp></td>
      <td><samp>and $rd, $rs, $rt</samp></td>
    </tr>
    <tr>
      <th scope="row"><i>Bitwise OR</i></th>
      <td><samp>$rd = $rs | $rt</samp></td>
      <td><samp>or $rd, $rs, $rt</samp></td>
    </tr>
    <tr>
      <th scope="row"><i>Bitwise XOR</i></th>
      <td><samp>$rd = $rs ^ $rt</samp></td>
      <td><samp>xor $rd, $rs, $rt</samp></td>
    </tr>
    <tr>
      <th scope="row"><i>Set on Less Than</i></th>
      <td><samp>$rd = $rs < $rt</samp></td>
      <td><samp>slt $rd, $rs, $rt</samp></td>
    </tr>
    <tr>
      <th scope="row"><i>Shift Left Logical</i></th>
      <td><samp>$rd, $rs << C5</samp></td>
      <td><samp>sll $rd, $rs, C5</samp></td>
    </tr>
    <tr>
      <th scope="row"><i>Shift Right Logical</i></th>
      <td><samp>$rd, $rs >> C5</samp></td>
      <td><samp>srl $rd, $rs, C5</samp></td>
    </tr>
  </tbody>
</table>
]

Note that there is no <samp>NOR<samp> operation due to the absence of such binary operation in C.
]

---

# MipC Language

.left-column[
#### Grammar
#### Arithmetic & Logic
#### Immediate
]
.right-column[
Additionally, there are the following immediate operations for some arithmetic and logic operations.

.smalltext[
<table class="table table-sm">
  <thead class="table-secondary">
    <tr>
      <th scope="col">Operation</th>
      <th scope="col">MipC</th>
      <th scope="col">MIPS</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th scope="row"><i>Addition</i></th>
      <td><samp>$rd = $rs + C16<sub>2s</sub></samp></td>
      <td><samp>addi $rd, $rs, C16<sub>2s</sub></samp></td>
    </tr>
    <tr>
      <th scope="row"><i>Bitwise AND</i></th>
      <td><samp>$rd = $rs & C16</samp></td>
      <td><samp>andi $rd, $rs, C16</samp></td>
    </tr>
    <tr>
      <th scope="row"><i>Bitwise OR</i></th>
      <td><samp>$rd = $rs | C16</samp></td>
      <td><samp>ori $rd, $rs, C16</samp></td>
    </tr>
    <tr>
      <th scope="row"><i>Bitwise XOR</i></th>
      <td><samp>$rd = $rs ^ C16</samp></td>
      <td><samp>xori $rd, $rs, C16</samp></td>
    </tr>
    <tr>
      <th scope="row"><i>Set on Less Than</i></th>
      <td><samp>$rd = $rs < C16</samp></td>
      <td><samp>slti $rd, $rs, C16</samp></td>
    </tr>
  </tbody>
</table>
]

* <samp>C16<sub>2s</sub></samp> are 16-bits 2s complement number.
    * Can also give hexadecimal pattern but both will be converted to signed value.
* <samp>C16</samp> are 16-bits binary number.
    * Can also give hexadecimal pattern and both will not be converted to signed value.
]

---

# MipC Language

.left-column[
#### Grammar
#### Arithmetic & Logic
#### Immediate
#### If Statement
]
.right-column[
Additionally, there are two kinds of if statement depending on the comparison:

.left-content[
#### MipC
```c
if($rs == $rt) {
  // then
}
```
```c
if($rs != $rt) {
  // then
}
```
]

.right-content[
#### MIPS
```asm
if_n: bne $rs, $rt, fi_n
      # then
fi_n:
```
```asm
if_n: beq $rs, $rt, fi_n
      # then
fi_n:
```
]

.smalltext[
The labels will be automatically generated with some numbers replacing the value of <samp>n</samp>.

The name of the opening labels are chosen to indicate the original operation (_e.g.,_ <samp>if_n</samp> for if statement) and the name of the closing labels are chosen as the ***reverse*** of the name of the opening labels (_e.g.,_ <samp>fi_n</samp> to match <samp>if_n</samp>).

The `# then` is a compilation of the then branch inserted within the matching labels.
]
]

---

# MipC Language

.left-column[
#### Grammar
#### Arithmetic & Logic
#### Immediate
#### If Statement
#### If-Else Statement
]
.right-column[
Additionally, there are two kinds of if-else statement depending on the comparison:

.left-content[
#### MipC
```c
if($rs == $rt) {
  // then
} else {
  // else
}
```
```c
if($rs != $rt) {
  // then
} else {
  // else
}
```
]

.right-content[
#### MIPS
```asm
if_n: bne $rs, $rt, el_n
      # then
      j   fi_n
el_n: # else
fi_n:
```
```asm
if_n: beq $rs, $rt, el_n
      # then
      j   fi_n
el_n: # else
fi_n:
```
]
]

---

# MipC Language

.left-column[
#### Grammar
#### Arithmetic & Logic
#### Immediate
#### If Statement
#### If-Else Statement
#### While Loop
]
.right-column[
Similarly, there are two kinds of while loop depending on the comparison:

.left-content[
#### MipC
```c
while ($rs == $rt) {
  // loop
  // body
}
```
```c
while ($rs != $rt) {
  // loop
  // body
}
```
]

.right-content[
#### MIPS
```asm
whl_n: bne $rs, $rt, lhw_n
       # body
       j   while_n
lhw_n:
```
```asm
whl_n: beq $rs, $rt, lhw_n
       # body
       j   while_n
lhw_n:
```
]
]

---

# MipC Language

.left-column[
#### Grammar
#### Arithmetic & Logic
#### Immediate
#### If Statement
#### If-Else Statement
#### While Loop
#### Do-While Loop
]
.right-column[
Similarly, there are two kinds of do-while loop depending on the comparison:

.left-content[
#### MipC
```c
do {
  // body
} while ($rs == $rt);
```
```c
do {
  // body
} while ($rs != $rt);
```
]

.right-content[
#### MIPS
```asm
do_n: # body
      beq $rs, $rt, do_n
od_n:
```
```asm
do_n: # body
      bne $rs, $rt, do_n
od_n:
```
]
]

---

# MipC Language

.left-column[
#### Grammar
#### Arithmetic & Logic
#### Immediate
#### If Statement
#### If-Else Statement
#### While Loop
#### Do-While Loop
#### For Loop
]
.right-column[
Lastly, there are two kinds of for loop depending on the comparison:

.left-content[
#### MipC
```c
for (init;$rs == $rt;updt) {

// body
  
}
```
```c
for (init;$rs != $rt;updt) {

// body
  
}
```
]

.right-content[
#### MIPS
```asm
       # init
for_n: bne $rs, $rt, rof_n
       # body
       # updt
rof_n:
```
```asm
       # init
for_n: beq $rs, $rt, rof_n
       # body
       # updt
rof_n:
```
]
.smalltext[
Unfortunately, both <samp>init</samp> and <samp>updt</samp> are required otherwise the compilation will fail.
]
]

---

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# End of File